Photographic fixer



Nov. 7, 1939. G. P. HAM

PHOTOGRAPHIC FIXER Filed June 10, 1939 FIQJ.

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BYQ s ATTORNEY.

Patented New. 7, 1939 UNM'ED STATES PATENT OFFICE PHOTOGRAPHIC FIXER Application June 10,1939, Serial No. 278,555

Claims.

This invention relates to a product for use in preparing photographic fixing baths. It particularly relates to a block of photographic fixing and hardening chemicals arranged in such a 5 manner that when placed in water they will dissolve in a predetermined order.

Photographic fixing baths in general use are aqueous solutions containing a fixing agent, acidifying agent and usually a hardening agent.. Sodium thiosulfate or thiosulfates are ordinarily used as fixing agents and usually associated with sodium sulfite as a preservative or antioxidant. Substances used as hardeners include potassium alum, potassium chrome alum, or similar compounds and for the acidifying agent acetic, citric, tartaric or similar acids may be used.

In the preparation of photographic acid hardening fixing baths it is necessary that the chemicals be dissolved in a definite order to prevent sulfurization or if potassium alum is used, precipitation of aluminum hydroxide. In the past these various compounds were supplied in individual packages, cartons, bottles, etc., and each compound was dissolved separately in the bath according to the order as directed by the formula. This method of packaging chemicals was satisfactory for supplying large commercial developers of photographs who, of course, have the proper facilities for weighing, measuring and preparing the fixing solutions. However, it is not satisfactory for the amateur photographic developers or for home development, becauseusually such persons do not have the proper facilities, time or inclination for weighing, measuring and 35 dissolving the various ingredients. As a result the baths are frequently spoiled, either because of dissolving the ingredients in the wrong order or adding an incompatible-ingredient before complete solution of the other ingredients.

' It has been known to combine the fixing chemicals in a single package and the hardening and acidifying chemicals in another package. In this case, it is only necessary to dissolve package #1 in a definite quantity of water and then dissolve package #2 in the same solution. .This method reduces the number of components to be dissolved but still requires that a definite order of mixing be followed to prevent sulfurlzation or in cases where potassium alum is used, a precipitation of aluminum hydroxide. Even when this order is followed, sulfurization or precipitation of aluminum hydroxide sometimes occurs and great care must be taken that package #1 is completely dissolved prior to the addition of package #2.

According to the present invention I have discovered a method whereby all the fixing components of a photographic acid hardening fixing bath are combined in a single solid composition and in such a manner that the various compo- 5 nents are selectively dissolved in a predetermined order when placed in an aqueous bath, without requiring any skill on the part of the operator.

The solid composition according to the'present invention may be in theform 'of a molded cube or .10 brick which is a convenient form for conserving space in packing and shipping. In another embodiment of the invention, the solid composition may be molded in the form of a sphere which permits complete solution of the concentric layer J of a component before any of the next component dissolves.

According to the present invention, the ingre dients of. the solid composition may be arranged individually in concentric layers or two or more 0 of the ingredients may be combined in a mixture and the mixtures thenarranged, according to any desired order, in layers.

It is an advantage of the present invention that a complete photographic fixer and hardener; 5

in a solid form requiring only solution in water is made available and a method is provided by which a photographic fixing bath can be prepared without danger of sulfurization or precipitation of aluminum hydroxide in cases where 30 potassium alum is used and without the necessity for weighing and measuring the various components.

Another important advantage is that the use of the product in preparing a photographic acid 35 hardening and fixing bath does not require any special precaution or care in order to obtain good results. It is only necessary to place a block in a measured quantity of water and allow it to dissolve. These blocks may be prepared in various and convenient sizes such as required for preparing a gallon, half gallon, quart or pint of the fixing and hardening bath.

In carrying out the present invention, all the chemicals necessary to prepare a photographic fixing and hardening bath are combined into a single block such that dissolution of the components in water follows an order that will prevent sulfurization or precipitation of aluminum hy- 50 droxide.

My invention will be specifically describedv with reference to the accompanying drawing in which Fig. 1 is an elevation showing a block of material in the torm of a sphere;

ing which is a layer 3 of a solid acid which in; turn is surrounded by a sodium sulfite layer 2 and an outer surrounding thiosulfate layer I.

When this form of the block is placed in a bath,

v5 the thiosulfate layer 1 will be completely dissolved before'any of the acid of layer 3 or the alum of core 4; hence, sulfurization or formation of aluminum hydroxide will not take place. In this form each layer will be completely dissolved before the next layer begins to dissolve.

Figs. 3 and 4 represent a form of the invention wherein a mixture of one group of ingredients is molded into a layer and a mixture of another group of ingredients is molded into an- :5 other layer. The core or central portion 6 is composes of alum or chrome alum and may contain part of the acid, upon which is molded an outer surrounding layer 5 consisting of a mixture of sodium sulfite and a thiosulfate with suflicient '0 acid present to prevent precipitation of aluminum hydroxide-if chrome alum is used. When this form of the block'is placed in water, the thiosulfate-sodium sulfite layer 5 will dissolve before the alum of layer 6 which may also contain 5 some acid. Therefore, sulfuriiation or formation of aluminum hydroxide cannot take place.

The blocks of Figs. 1 and 3 as described abovemaybe produced by the usual molding methods. The ingredients may be -used either in the powder or crystalline form; when the powdered form is used, less pressure is required to mold but the rate of dissolution is usually slower. Substances that are inert photographically may be used as binders to aid in molding or to increase the rate of disintegration and dissolution in water. The outer layer may be made of crystalline sodium thiosulfate but requires greater pressure than when a mixture of anhydrous and crystalline thiosulfate is used. The presence of the anhydrous thio'sulfate would also permit the block to be moistened prior to molding in which case the amount of pressure is less and a hard smooth surface is produced upon drying. When the mixture of anhydrous and crystalline sodium thiosulfate is subjected to moisture and then molded a hard smooth surface is produced but throughout the rest of the layer there are formed chan nels or small air spaces. These channels or air spaces seem to increase or aid in the dissolution of such a block, because as soon as the smooth outer surface is dissolved, the water will pass into the channels and throughout the entire layer of sodium thiosulfate.

The following examples are illustrations of methods by which the invention is carried out in connection with a specific acid hardening fixing bath formula. However, this particular formula is used for purposes of illustration only and is not to be construed as limiting the invention.

Example 1 23.81 grams of potassium aluminum sulfate were molded into a core 4 as indicated in Fig. 2. Then a mixture of 10.56 grams of citric acid, 0.81

gram of sodium acid phosphate and 0.18 gram of anhydrous sodium sulfite was molded onto and surrounding the core 4, to form layer 3. Next a mixture of 17.92 grams of sodium acetate and 15.36 grams of anhydrous sodium sulfite was molded into position as indicated by the layer 2 and finally a mixture of 74.24 grams of sodium thiosulfate and 148.48 grams of anhydrous sodium thiosulfate was molded in position to form the outer shell I.

The above block was dropped in one liter of waterat 125 F. and allowed to dissolve. Selective dissolution was enacted as indicated by the fact that no sulfurization or precipitation of aluminumhydroxide occurred. Sulfurization or formation of aluminum hydroxide would generally occur if a portion of the acid or alum dissolved prior to the sodium thiosulfate.

Example 2 A mixture of 23.81 grams of potassium aluminum sulfate, 0.18 gram of anhydrous sodium sulfite, 10.66 grams of citric acid and 0.81 gram of sodium acid phosphate was molded into a core or inner portion 6 as indicated in Fig. 4. Then a mixture of 74.24 grams of sodium thiosulfate, 148.48 grams-of anhydrous sodium thiosuliate, 15.36 grams of sodium sulfite and 17.92 grams of sodium acetate was molded onto and surrounding core 6, to form the outer shell or layer 5. This cube was dropped in one liter of water at 125 F. and allowed to dissolve. There was no sulfurization of precipitation of aluminum hydroxide which indicated that the thiosulfate of shell 5 dissolved before the alum or acid of the core 6.

It is to be understood that certain photographically inert substances may be added to the various components to assist in molding and that any layer of the component may be coated with a soluble photographically inert material prior to theapplication of the next layer. Various degrees of pressure may be applied in forming the layers and with intervention of other substances that will aid in dissolution.

What I claim is:

1. A photographic fixing and hardening composition in the form of a solid mass comprising a core of hardening component surrounded by a layer of fixing component.

2. A composition for use in photographic fixing and hardening comprising a molded solid mass of the hardener surrounded by a solid molded mass of the fixer.

3. A composition in the form of a block for use in photographic fixing and hardening comprising an inner core of a mixture of acid and an alum surrounded by a layer of a mixture of sodium thiosulfate, sodium sulfite, and an acid.

4. A solid molded composition for use in photographic fixing and hardening consisting of an inner core of an alum surrounded by -a layer of an acid, said acid layer surrounded by a layer of sodium sulfite and an outer layer of a thiosulfate, each layer being of substantially uniform thick:

ness.

5. A photographic fixing and hardening composition in a solid form which comprises a molded alum core upon which is then molded in successive surrounding layers an acid, a sulfite and sodium thiosulfate in such a manner that the outermost layers will dissolve in succession in a water bath, each layer being of substantially uniform thickness.

GARNET PHILIP HAM. 

